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2015 Perennial Plant of the Year - Geranium x cantabrigiense 'Biokovo'

Geranium X cantabrigiense 'Biokovo' in flowerThe Perennial Plant Association membership has voted and the 2015 Perennial Plant of the Year™ is  Geranium X cantabrigiense ‘Biokovo’. 

’Biokovo’ is a naturally occurring hybrid of Geranium dalmaticum and Geranium macrorrhizum found in the Dalmatia region of present-day Croatia.  It blooms in late spring with masses of 5-petaled white flowers, about ¾” diameter, that are tinged pink at the base of each petal and have darker pink center stamens. An interesting feature is that the sepals that are redder than the petals, so that when the flower opens the lightly tinged pink flowers provide a nice contrast to the sepals and stamens.  It blooms from mid-May to late July.
G. X cantabrigiense has aromatic foliage and rounded leaf edges and is semi-evergreen in most climates.  It has a spreading habit and is rhizomatous, i.e. it spreads by sending out runners.  It grows to 6-10 inches high, with a spread of about 2 feet.  It can be used as a ground cover that spreads fairly rapidly through the perennial bed or as an edger in the front of the border.  It also does well in rock gardens.  It tolerates full sun to part-shade conditions.  Its foliage turns scarlet and orange in the fall. 


Another G. X cantabrigiense variety is 'Karmina', because sometimes it matters what color the flowers are!

Geranium X cantabrigiense 'Karmina', seen below, has carmine-red flowers.


The general qualities of Geranium species (commone name "cranesbill") include: 

  • Deer Resistant (OK, yes, nothing is completely deer-resistant; it is in many places I've planted it)
  • Many varieties tolerate some shade
  • Bloom for 4 weeks or more 
  • Rabbit Resistant (again, it depends, but in general they leave it alone)
  • Flowers attract butterflies
  • Can be used as groundcovers (low spreaders) or bed-fillers (taller varieties)
  • Need little care and no division
  • Excellent mounding habit as they first start in spring, and some varieties maintain that habit.  
  • Deeply cut foliage; flowers with interesting veining patterns. 
  • They can be deadheaded after blooming, or the tops of the plants can be sheared back to new growth to stimulate re-bloom and freshen foliage.  
  • Many varieties have beautiful red, burgundy or orange fall color that is a stand-out if the plant has been allowed to weave intself throught the garden bed.

Other types of geranium that are useful in different garden contexts, are hardy and fairly care-free include:

  • Geranium macrorrhizum (Bigroot Geranium), Z 3-8, 15-18" in height, native to southern Europe, large laromatic leaves.  Varieties include 'Bevan's Variety' and 'Ingwersen's Variety', seen in the series of pictures below:


G. macrorrhizum 'Bevan's Variety'

G. macrorrhizhum 'Ingwersen's Variety'Photo Credit: Kathy Diemer "A Garden for All". 'Bevan's Variety' and 'Ingwersen's Variety growing side-by-side; in case flower color matters!

 G. macrorrhizum fall foliage color


  • Geranium pratense (Meadow Cranesbill), Z 5-7, 24-36" tall, purple flowers from reddish veins on dark blue petals, native to northern Europe, may need staking.  Some cultivars have dark foliage; need sun for optimal foliage color.   Clump-former; blooms May – July.  Cultivars include 'Dark Reiter',  'Midnight Reiter', 'Summer Skies', 'Purple Haze', 'Mrs. Kendall Clark', 'Splish Splash'.  G. praetense does spread by seed, so it can pop up here and there throughout the garden - that may be a desirable trait if you're trying to get it to fill in, or an undesirable trait if you only want it in a certain place.



G. praetense 'Midnight Reiter'


  • Geranium sanguineum (Bloody Cranesbill) Z 3-8, 9-12", magenta flowers in spring, native to Europe and Asia, tolerates heat and drought; deeply divided leaves, bright red fall color, blooms in spring.  Varieties include 'Striatum', 'Max Frei', 'Ankum's Pride'.


G. sanguineum 'Max Frei'

G. sanguineum var. striatum 

  • Geranium wlassovianum Z 5-8, 18-24" tall; One of the first hardy Geraniums to bloom and one of the last to stop. Dusky violet flowers with deeper veining and a white eye. Fall brings outstanding deep red tones. Trails gently.  Will adapt to most soil conditions provided there is good drainage and some moisture. Nice massed as a groundcover, in rock gardens or as an informal edger. Completely carefree.


G. wlassovianumG. wlassovianum fall foliage color


  •  And, of course, Geranium X 'Rozeanne' seen below.  Unbelievable quantities of large, violet-blue blooms from June until frost; hardy to Z5; 20" tall with a 2 foot spread; bluish-purple flowers are heightened by black anthers, magenta veins and a radiant white eye. Fiery red leaves in autumn; withstands sunny, hot sites and is happy just about anywhere, from an exposed border to a container.  'Rozeanne' is a naturally occurring sterile hybrid of Geranium himalayense and Geranium wallichianum ‘Buxton’s Variety’.  Lynden Miller says "No garden should be without Geranium 'Rozeanne'."




Insect Hotels


One of the things that everyone's been thinking about in the world of landscape design is how to protect the pollinators and encourage "good bugs" so that our gardens and landscapes will be healthier and more sustainable.  Some homeowners are in the habit of "cleaning up" the garden within an inch of its life, leaving no leaf litter or dormant perennial stalks, no fallen trees or piles of sticks - blowing it all away down to the bare dirt.  This may create a "tidy" look, and it may "take less time" to use a leaf blower than a rake, but there are SO MANY reasons not to do this!  Leaving aside the air and noise pollution created by leaf blowers, their health hazards to those who use them, and the soil compaction that results from having 180 mph hot air blown at it - what about the habitat that's being taken away?

Insects of all kinds need places to overwinter and to create their nests.  If there are no nooks and crannies, no hollow stems, no rotting logs, no decaying leaves available, those pollinators and beneficial bugs will leave your yard and find somewhere else to be.  Poof - no pollination for you!

The good news is that you can create habitats for beneficial insects by collecting natural or salvaged materials into one place, where multiple types of insects can overwinter and nest.  They're easy and fun to make yourself, and can become works of art if you want them to be.  Maybe more attractive and effective in a small yard than keeping a not-very-extensive "wild area" somewhere.  You may have to replace some of the elements every late-summer, but its a great way to "recycle" old bricks, leftover stone, tile shingles or old crates.  You can make pruned branches or old firewood into art just by arranging it in an orderly fashion.  Add some pinecones and some cut pieces of bamboo.  If you have leftover wood, drill holes into a block of wood to create habitat for bees who nest in hollows.

If you google "insect hotel" you'll come up with some pictures and some instructions - then let your imagination take over.  Pay attention, though, to where to place (or to build) your insect hotel once its finished - the insects will need afternoon sun to keep warm.

Here's a simple example about how stacking some old bricks in an unused part of your garden bed then inserting twigs, hollow stems and dried grasses in an orderly fashion creates both art and habitat.

These are some of the elements you can include:

  • A compartment with a red-colored slitted door filled with wheat straw will attract Green lacewings, ladybugs and earwigs and provide them with a place to hibernate from the middle of September until early April. Lacewings devour aphids and other pests such as scale insects, many types of caterpillar and mites.  Another way to make a good lacewing habitat is by rolling up a piece of corrugated cardboard and putting it in a waterproof cylinder, such as an old plastic bottle. 
  • Lots of different kinds of bees make their nests in hollow sticks, hollow plant stems or holes in wood made by wood-boring insects.  Mason bees (Osmia), masked bees (Hylaeus) and solitary wild bees all will use different diameters of holes.  There are many different species of solitary bee, all are excellent pollinators. The female bee lays an egg on top of a mass of pollen at the end of a hollow tube, she then seals the entrance with a plug of mud.  A long tube can hold several such cells.   
  • A compartment filled with pine cones provides lots of safe spaces for lots of differenet insects, including garden spiders.
  • Dead wood is an increasingly rare habitat as we tidy our gardens, parks and woodlands. It is essential for the larvae of wood-boring beetles, such as the stag beetle.  It also supports many fungi, which help break down the woody material.  Crevices under the bark hold centipedes and woodlice.  Place rotting logs at the base of your hotel so the logs stay nice and damp and mix with other decaying plant matter to attract centipedes (which devour slugs) and other woodland litter insects such as millipedes and woodlice (which will provide a welcome source of food for birds). This is also a great spot for garden spiders.
  • Frog hole.  Frogs eat many slugs and other garden pests.  Although they need a pond to breed in, they can spend most of the year out of water.  We use stone and tiles as these provide the cool damp conditions amphibians need.  Newts may also take advantage of these conditions.  Amphibians need a frost-free place to spend the winter; this could be in the center of the habitat you create, inside the base of a dry-stone wall, under a pile of rubble or deep underground. 
  • Straw and Hay provide many opportunities for invertebrates to burrow in and find safe hibernation sites. 
  • Twigs, sticks and stems: Bundled together, sticks and twigs of different sizes offer welcome lodgings for ground beetles. These beetles chomp away at many of the pests that attack our crops, including aphids and carrot root fly larvae.  You'll also be offering a vacancy to ladybugs, which eat aphids and mites.  The adults hibernate over winter; they need dry sticks or leaves to hide in. Hoverflies will also be attracted to this type of material.  Hoverflies are both pollinator and pest patroller – the larvae carry an insatiable appetite for aphids while the adults feed on nectar as they pollinate flowers.
  • Loose bark is a habitat for beetles, centipedes, spiders and woodlice, who all lurk underneath the decaying wood and bark. They help to break down woody plant material and recycle it back into compost.
  • Dry leaves mimic the litter on the forest floor and provide homes for a variety of invertebrates.
  • Crevices are important places for hibernation through the winter.  Make sure your insect hotel has plenty of different types of crannies and crevices.
  • Bumblebees. Every spring queen bumblebees search for a site to build a nest and found a new colony. An upturned flowerpot in a warm sheltered place might be used. 


Seen below in the picture is a FABULOUS idea - incorporate both a mini "green roof" and insect habitat to construct a decorative stacked-stone wall.  This one looks like it might be one of two that define an entry into the next garden room - which looks like it might be a meadow.

Which reminds us that we need larval foods and nectar-producing flowers as part of the habitat as well.  Make 2015 the year when you do something artistic and whimsical to protect the pollinators!



Winter Dormancy and Cold-Hardiness - How woody plants survive winter

Apple flower bud in spring

Winter dormancy of woody plants is based on their ability to track photoperiod, air temperature and soil temperature.  Once in a dormant state, the plant goes on to develop cold resistance, also referred to as "cold-hardening" or "cold-hardiness".  Dormancy happens before the cold-hardening process starts, usually in about September for woody plants.  The first stage of dormancy is called "endodormancy" – plants stop growing so that they can reconfigure their gene expression towards the acquisition of cold tolerance.  During endodormancy, internal signals and processes within the plant prevent growth, even if the plant is returned to growth-promoting external conditions.  In other words, during endodormancy buds simply can't grow.  This prevents the initiation of new shoot growth from buds in autumn, when the environment can rapidly fluctuate between growth-promoting and non-promoting conditions – that would be a waste of precious energy for the plant.

Cold-hardening* refers to environmentally- and hormonally-regulated changes in gene expression that lead to changes in metabolism and cellular functioning to protect cells from damage due to dehydration and freezing.  It occurs in two stages over a period of weeks to months.  Stage 1 occurs when temperatures are between 10 - 20 °C (50 – 68 °F) and includes a shift on gene expression towards storage of reserve carbohydrates and lipids.  Stage 2 is promoted by colder temperatures and involves the accumulation of cryoprotectant substances (natural "antifreeze"), as well as changes in membrane lipids and structural changes in bud anatomy.  Because cold-hardening requires energy, a plant may not be able to become fully cold-hardened if it is diseased or stressed such that there are low amounts of reserve carbohydrates.

Bud dormancy is only broken by exposure to cold temperatures – i.e. by a period of chilling.  The plant senses "chill" (temperatures below "biological zero" 41 °F; 5 °C).  Although freezing is not required, freezing temperatures during endodormancy can break dormancy faster.  Likewise, intermittent warm days during endodormancy delay dormancy release.  Between 1000 and 2000 hours of chilling are required for most woody plants in temperate zones, varying by species.  A combination of photoperiod (increasing day length) and adequate chilling leads to dormancy release.  The buds now enter a period referred to as "ecodormancy" – meaning that growth is arrested by environmental conditions that are not conducive to growth.  As soon as conditions become favorable, growth can occur.

The overall process goes something like this:

 • The plant needs to form buds so that it can generate vegetative growth (leaves) next year, because leaves are where photosynthesis occurs – i.e. where food is made by the plant.  Setting buds requires the plant to use energy, and occurs during the plant's active growth period.

• Bud formation is signaled by plant hormones under the control of temperature and photoperiod.   

As days shorten and temperatures decrease, buds enter a dormant state (endodormancy), during which they stop growing and instead develop cold resistance – a metabolic process that requires the plant to use its energy reserves.  Plants break down proteins and other chemicals that were stored in their leaves during the growing season and store them in buds, bark and wood for growth next spring.  These stored forms of energy will function when temperatures are near-freezing and can survive freezing and thawing in the winter.  
• One consequence of this change in metabolism in many woodies is a change in leaf color – accessory pigments that helped protect chlorophyll from sunlight damage are released and become visible.
During this period of endodormancy, buds cannot grow, and that's a way that the plant protects itself from expending energy on growth that will more than likely be killed by cold temperatures.
Buds need extended both exposure to cold temperatures ("chilling") and increasing day length to break dormancy and re-establish their growth competence.
On fruit trees, if the buds do not receive adequate chilling, there will be no flowers and no fruit.  Fruit tree breeders are developing low-chill-requiring cultivars so that as global warming progresses fruit can still be grown in temperate climates.
When photoperiod and chill requirements have been met, buds break endodormancy.  Nonetheless, buds remain "ecodormant" – i.e. capable of growth but not actively growing – until they are exposed to warm temperatures (both soil and air) for a critical period before shoot extension and initial leaf emergence.  This is an energy-requiring process that draws on the plant's energy reserves.  Once new leaves begin to emerge, they are susceptible to being killed by frost.
 • Within a given species, there can be both northern and southern "eco-types" with different chilling requirements.  For example, while a red maple from a cold part of its range may need 2000 hours of chilling to break endodormancy, a red maple from a warm part of its range may need less than 1000 hours of chilling.  If you transplant a red maple grown in the warmer part of its range to the colder part of its range, it will only be in ecodormancy during most of the winter (because its chill requirement is quickly met and then its endodormancy is governed only by photoperiod).  If the winter is mild, it may leaf out, then have those leaves killed by a spring frost.  The maple grown in the cold part of its range and transplanted to another location in the cold part of its range will have a chill requirement that means it will remain endodormant longer during a mild winter, and therefore be less likely to leaf out "early". 

Phenological Stages of apple fruit production


*Footnote: "Cold-hardening" is not to be confused with "hardiness zone".  Saying that a plant is "cold-hardy to Zone 4", for example, describes its potential to be able to resist cold damage – i.e. the lowest temperature it can withstand – a function of its particular genetic make-up.  However, even "cold-hardy" plants must undergo the "cold-hardening" process over and over again each winter.




Stages of Highbush Blueberry Fruit Production



Frost is beautiful

Frosted crabapplesFrosted grass seedheadsFrosted lacecap hydrangesFrosted formal garden


Incorporate your late fall clean-up “trimmings” with other natural materials for a one-of-a-kind seasonal wreath

The weather was very mild in late November and early December, after an early cold snap, so fall clean-up chores extended into the holiday-decorating-of-containers season this year.  I realized that some of the stuff I was “cleaning up” could be used to decorate the containers or added to wreaths.  My favorite garden pictures website is GAP Photos (www.gapphotos.com) – it’s a British site and always features projects that can be done with natural materials.  Here are a few of the wreath ideas that were on their blog this winter:

'Hedgerow" wreath

This one they call the “hedgerow” wreath.  Since I am dedicated to the proposition of creating hedgerow-like plantings for any of my clients who are willing, this showed me how beautiful the fruits of a hedgerow can be (for people).  Of course, birds and animals love hedgerows too.  This wreath has Malus (crabapples), Crataegus (hawthorn), Rosa (rose hips) and Rubus (blackberry) and some other types of dried seedheads.
Features of a Hedgerow
Most hedges in Britain were originally planted to keep grazing animals contained. They include one or several shrub species, often planted on a bank or with an adjacent ditch. Mixed hedgerows may include tree and shrub species such as hawthorn, hazel (Coryllus avellana), Field maple (Acer campestre), and oak.  An “American” version might include serviceberry (Amelanchier), paperbark maple (Acer griseum) (for a beautiful winter bark), corneliancherry dogwood (Cornus mas) and shrubs like highbush blueberry (Vaccinium corymbosum), red-twig dogwood (Cornus sericea), bloodtwig dogwood (Cornus sanguinea), smokebush (Cotinus coggygria) or ninebark (Physocarpus opulifolius).  You could plant Corylus colurna (Turkish hazel) instead of Corylus avellana (hazel as in hazel nuts).  I’ve also planted giant dogwood (Cornus controversa) and pagoda dogwood (Cornus alternifolia) in a “hedgerow” (I call it a mixed screening border).  For a little pizazz you could add a crapemyrtle (Lagerstromia).  Mix in a few evergreens like American holly (Ilex opaca), Oriental spruce (Picea orientalis) and slow-growing blue spruce (Picea pungens ‘Fat Albert’).
Habitat for wildlife
Tall, wide and bushy hedges with several different plant species provide the richest wildlife habitats. The thick vegetation they offer gives shelter to nesting and hibernating animals while hedgerow flowers, fruits and nuts are a food source for invertebrates, birds and small mammals. Hedges act as corridors for small creatures to travel along under protective vegetation.


Some additional wildlife-friendly and/or sustainability-friendly wreath ideas:

Crabapples wired together in a circle

Maple leaves or other colored fall leaves wired into a circle.

You can cut a few stems of red-twig dogwood and winterberry holly to stuff into your containers.  If you prune your magnolias, you can use their branches in containers as well.  I’ve put dried-on-the-shrub hydrangeas that have nice colors into windowboxes and containers as well.

At my house I added a bittersweet-from-the-roadside wreath on the gate and red-twig and yellow-twig dogwood stems with winterberry holly stems in the containers.  I also have the beautiful winter silhouette of climbing hydrangea that “camouflages” part of the dreaded chain-link fence.